1. Field of the Invention
The present invention relates to a control method for bidirectional DC-DC converters. More particularly, the present invention relates to the control method for bidirectional DC-DC converters for enhancing the power conversion efficiency.
2. Description of the Related Art
U.S. Patent Pub. No. 20090059622, entitled “Bi-directional DC-DC Converter and Method for Controlling the Same,” discloses a bi-directional DC-DC converter having a transformer for connecting a voltage type full bridge circuit connected to a first power source and a current type switching circuit connected to a second power source. A voltage clamping circuit constructed by switching elements and a clamping capacitor are connected to the current type switching circuit. The converter has a control circuit for cooperatively making the switching elements operative to control a current flowing in a resonance reactor.
Another U.S. Patent Pub. No. 20120098341, entitled “Bidirectional DC-DC Converter and Control Method Thereof,” discloses a small-size, high-efficiency, isolated, bidirectional DC-DC converter. The bidirectional DC-DC converter includes a transformer in which windings are magnetically coupled, switching circuits, a diode connected in parallel with a switch, smoothing capacitors, and a control section. The first and second DC power supplies, which are connected in parallel with the smoothing capacitors, respectively, provide bidirectional electrical power transfer. When electrical power is to be transferred from the first DC power supply to the second DC power supply, the switch is maintained in the ON state. When, on the other hand, electrical power is to be transferred from the second DC power supply to the first DC power supply, the switch is maintained in the OFF state to prevent a reverse electrical power flow from the first DC power supply.
However, there is a need of improving the control method for bidirectional DC-DC converters disclosed in U.S. Patent Pub. No. 20090059622 and U.S. Patent Pub. No. 20120098341 for enhancing the power conversion efficiency and reducing the manufacturing cost. The above-mentioned patent publications are incorporated herein by reference for purposes including, but not limited to, indicating the background of the present invention and illustrating the state of the art.
As is described in greater detail below, the present invention provides a control method for bidirectional DC-DC converters. When the bidirectional DC-DC converter is operated, a boost mode or a buck mode of the bidirectional DC-DC converter is adjusted to reduce power loss in such a way to mitigate and overcome the above problems.